INTRODUCTION 9 



afterwards discovered, is composed of the remains 

 of minute forms of animal life known as animalculas. 

 It also contains shells and the teeth and bones of 

 larger animals. The "Challenger" expedition dis- 

 covered, too, by a long series of soundings, that 

 the deepest part of the ocean, away in the far 

 Pacific, was 4,500 fathoms, or 27,000 feet. More 

 recent soundings, however, have given the deepest 

 part of the Pacific Ocean as over 32,000 feet, or 

 slightly more than six miles. Can we realise 

 what this really means ? If we could take Mount 

 Everest, in India, the highest mountain peak in 

 the world, and place it in the deepest part of 

 the Pacific Ocean, the peak would be three 

 thousand feet below the level of the ocean. 



Another important fact ascertained by the 

 " Challenger " expedition was that the bed of the 

 ocean is uneven, like the surface of the land ; 

 there are peaks and valleys under the ocean 

 similar to those with which we are familiar. The 

 enormous collections that were brought home by 

 the expedition were subsequently studied and 

 described by well-known specialists belonging to 

 nearly every civilised nation. Some idea of the 

 importance and value of the expedition may be 

 gathered from the fact that the official records and 

 descriptions fill fifty bulky volumes. 



No sunlight whatever penetrates the deepest 

 parts of the ocean. Probably all is dark below 

 two hundred fathoms, i.e., twelve hundred feet, 

 except the small degree of light emitted by the 



